Copyright © The Author 2007. Published by Oxford University Press.
A Concordance Invariant from the Floer Homology of Double Branched Covers
1 Department of Mathematics, Columbia University New York, NY 10027, USA
2 Department of Mathematics, Louisiana State University, Baton Rouge, LA 70803, USA
Correspondence: Correspondence to be sent to: Ciprian Manolescu, Department of Mathematics, Columbia University New York, NY 10027, USA. e-mail: cm{at}math.columbia.edu
Ozsváth and Szabó defined an analog of the Frøyshov invariant in the form of a correction term for the grading in Heegaard Floer homology. Applying this to the double cover of the 3-sphere branched over a knot K, we obtain an invariant
of knot concordance. We show that
is determined by the signature for alternating knots and knots with up to nine crossings, and conjecture a similar relation for all H-thin knots. We also use
to prove that for all knots K with
(K) > 0, the positive untwisted double of K is not smoothly slice.